Vertical glass panels such as doors or wall partitions typically have bottom and top edges that are secured within horizontal rails. The vertical edges of the glass panels may be left free or may be secured within vertical stile, mullion, or door or wall jamb members for additional protection. The framing members are typically made from lightweight materials such as aluminum and are provided with decorative finishes or covers to create a pleasing ornamental appearance. The appeal of glass panel framing systems has been limited however, by the difficulty and cost of installing known systems and by the costs and inconvenience of repairing a damaged or marred glass framing member after initial installation.
In many common structural glass panel framing systems, glass panels are fitted into channels formed within the rails, stiles, mullions and door/wall jamb assemblies and secured within the framing members by means of an adhesive sealant. This type of construction makes it difficult or impossible to remove the framing member from the panel after the adhesive sealant has cured. The inability to readily remove a framing member for replacement is generally considered to be a disadvantage of these permanent attachment designs because, over time, the framing members and/or glass become marred from use and replacement is desirable in many commercial applications to maintain aesthetics. The installation of permanent attachment designs also requires substantial skilled labor and time at the job site.
To address some of the disadvantages of prior art permanent attachment framing systems, designs that clamp onto the glass panels have been developed. These new designs have allowed for the ready replacement of damaged framing members and/or glass panels and have reduced the time required to frame glass panels. Several such clamp-on rail, stile, mullion and wall/door jamb designs have been developed. Generally, each type relies upon the application of clamping force to retain a glass panel within a channel which forms part of the framing member. The clamping action is typically produced either by screws bearing directly against clamping strips which bear against the glass panes or by wedging action whereby wedge blocks are pulled downwardly or pushed upwardly against mating angled walls to force the blocks inwardly against the glass panels to create clamping pressure.
One drawback of the prior art clamping systems for attaching framing members to glass panes is the inability to precisely control the degree of clamping force applied to the panes. This problem is of particular concern in the installation of insulated glass panels. Insulated glass panels typically comprise two glass panes which are separated by a spacer. Problems occur because the spacer is often hollow to reduce weight and may be crushed if overstressed during installation of the framing members. In addition the individual glass panes used in insulated glass panels are generally substantially thinner than the panes of conventional single glass panels and hence are more subject to cracking during the installation of framing members.
Despite improvements in the glass panel framing art, there remains a need for structural glass framing members that are easy to install, allow for the replacement of component parts, and which maintain a uniform, controlled, clamping pressure on the glass panes.